The invention relates to a device or devices for sensing specified conditions in and out of fluid and has particular application as a swimming pool alert alarm for sensing persons or animals in or around the swimming pool as well as sensing a man overboard.
There are a number of sensing devices for this purpose available at least in the prior art. Some of these devices are as follows:
U.S. Pat. No. 3,054,096 awarded to S. Peritz teaches an emergency alarm particularly adaptable for use in a swimming pool. The device is adapted to float on the surface of the water and includes a pendulum which activates an audio alarm when sufficient water motion moves the pendulum to complete the alarm energizing circuit connected thereto. This device has certain drawbacks, namely, it is wind activated as well as by objects falling into the pool water and is an obstruction to authorized users of the swimming pool. If the device were adjusted whereby all but strong wind gusts were not detected then small children or animals would most probably not be detected either. The electrical circuit could be exposed to water rendering the device inoperable.
U.S. Pat. No. 3,475,746, awarded to inventors L. H. Nelson et al., teaches a self contained device that floats freely on the surface of a pool or the like. When the liquid in the pool is disturbed, a flexible diaphragm responds to pneumatic pressure producing a chamber containing air by wave motion to actuate a signaling device which continues to operate until turned off. This teaching encounters the same problems as the Peritz Patent discussed above.
U.S. Pat. No. 3,486,166, awarded to inventors N. L. Campana et al., teaches an alarm system for swimming pools which operates by submerging the sensing means (hydrophone) into the pool water. This system could only be installed at great economic expense to the pool owner and could not be removed from the pool for use elsewhere, etc.
U.S. Pat. No. 3,808,887, awarded to Albert T. Buttress, teaches the use of fibre optics to monitor liquid levels in a light transparent tank. This reference does not teach the use of fibre optics submerged in a liquid for measuring surface impact of that liquid.
U.S. Pat. No. 4,187,502, awarded to Frank O. Beverly et al., teaches a swimming pool alarm with a pressure transducer immersed into the swimming pool water. This system is expensive to produce, places the electronics in a position susceptible to water damage and could be triggered by external noise.
U.S. Pat. No. 4,408,193, awarded to Theodore I. Millen, teaches a swimming pool alarm system which monitors wave motion. This system has the obvious wind generated wave problems discussed above.
There has not been a completely successful swimming pool alarm system until the emergence of this invention.